The dorsal vessel of the stick insect
Baculum extradentatumconsists of a tubular heart and an aorta that extends anteriorly into the head. Alary muscles, associated with the heart, are anchored to the body wall with attachments to the dorsal diaphragm. Alary muscle contraction draws hemolymph into the heart through incurrent ostia. Hemolymph exits the heart through the excurrent ostia present on the dorsal vessel in thoracic and abdominal segments. FMRFamide‐related peptides are present in axons of the segmental nerves that project to the dorsal vessel and in processes extending over the heart and alary muscles. Immunoreactive processes are also localized to the valves of the incurrent ostia and excurrent ostia and to the lateral cardiac nerve and lateral cardiac neurons.